50 JULY 2011 water
SWWS Workshop: Emerging Trends
and Issues in Decentralised Water
and Wastewater Systems
Reported by P Devellerez and K Dahl
As part of the Ozwater'11 Conference, the Small Water
and Wastewater Systems (SWWS) Specialist Network
successfully conducted a workshop on 'Emerging trends
and issues in decentralised water and wastewater
systems'. More than 50 delegates attended the workshop.
Three speakers presented on a number of case studies
and the changing market for decentralised systems. This
was followed by a broad group discussion on strengths,
weaknesses and opportunities of decentralised systems.
Workshop Overview
Over the past 100 years the water industry has moved
towards centralisation in order to achieve economies of
scale in infrastructure construction/operation and the required
public health objectives. Decentralised systems were often
seen as temporary solutions until the centralised system
became available. Today, however, the role of decentralised
systems is changing due to a number of reasons, including:
• Increasing pressure on water supplies, resulting in the
need to consider alternate water sources and local
treatment/local reuse;
• Increasing environmental and health requirements,
resulting in the need to improve water quality;
• Availability and viability of innovative technologies;
• Increasing regulation around the operation of decentralised
systems and changing regulatory regimes for private
decentralised systems;
• Increasing costs of centralisation associated with
urban sprawl;
• Increasing loads on existing infrastructure through
infill development.
Centralised water and wastewater systems, and sourcing
of water and treatment of wastewater outside of the main
urban area, have traditionally delivered important benefits to
society, particularly in the improvement of health. This traditional
paradigm for water services is being challenged by rapid urban
growth, capacity-constrained infrastructure, limited water
resources and uncertainty associated with climate change.
These challenges have prompted the consideration of
alternative approaches in meeting the demand on water
services, and decentralised systems are increasingly
regarded as important components for the transition
to more sustainable solutions.
Where existing water and wastewater service infrastructure
are close to design capacity and cannot meet the demands
of proposed developments, decentralised systems are often
a viable option to reduce the pressure on existing services,
thus deferring the immediate need to upgrade the infrastructure.
Decentralised services can exploit multiple water sources,
such as rainwater, stormwater and recycled wastewater. There
is a real potential for improved environmental protection by
minimising the impact of discharges and large volume transfer
that may harm ecologically significant areas.
The potential to adopt innovative technologies and also
develop proof-of-concept in decentralised developments has
traditionally been an important driver in many systems, deferring
infrastructure upgrades by allowing a staged investment in
decentralised infrastructure in areas that are at capacity,
or remote from existing centralised services.
Decentralised systems facilitate the adoption of alternative
water supply and maximum benefit through reuse of water
streams preserving potable supplies.
The suitability of decentralised systems needs to be
assessed in the planning process for appropriateness to meet
both short- and long-term water service needs. Major factors
to be considered include population size and density, housing
types, community facilities, and the mix of land uses such
as residential, commercial and industrial. Populations that
fluctuate, such as at holiday resorts, can also impact on
the suitability of decentralised water systems.
Workshop Presentations
Kurt Dahl, of Permeate Partners, set the scene for the workshop
by briefly presenting four case studies on the following topics:
Sewer mining at Pennant Hills Golf Club (NSW) (sewer
mining from a 350mm sewer which runs through the golf
course): This option was selected as it could provide a reliable
supply, and the technology to produce high-quality recycled
water was proven in similar applications. The main disadvantage
was the lack of precedent in Sydney. Since commissioning in
March 2008, the sewer mining facility has met or exceeded all
expectations. It has set the benchmark for sewer mining
in Sydney and around Australia.
Groundwater and stormwater at Royal Melbourne Golf Club
(Vic): To eliminate its reliance on potable water, in January 2010
RMGC implemented what became known as the 'Water for
Irrigation' project, which consisted of four main elements:
• Upgrade of groundwater reticulation infrastructure to
improve yield;
• Construction of membrane filtration, reverse osmosis and
chlorination systems to disinfect and reduce salt levels in
the irrigation water;
Kurt Dahl of Permeate Partners presented a range of case studies
describing decentralised systems in NSW, Victoria and WA.
-- Special Report
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